Instrument for sensing the densities of fluids



Jan. 5, 1954 D. H M DONALD INSTRUMENT FOR SENSING THE DENSITIES OF FLUIDS Filed Jan. 4, 1951 3 Sheets-Sheet l Mi d Jan. 5, 1954 D. H. Ma DONALD INSTRUMENT FOR SENSING THE DENSITIES OF FLUIDS Filed Jan. 4, 1951 5 Sheets-Sheet 2 Jan. 5, 1954 D. H. M DONALD INSTRUMENT FOR SENSING THE DENSITIES OF FLUIDS Filed Jan. 4, 1951 3 Sheets-Sheet I5 Patented Jan. 5, 19:54

INSTRUMENT FOR SENSING THE DEN SITIES OF FLUIDS Dennison H. MacDonald, East Haven, Conn., as-

s gnor to Revere Corporation of America, Wallingford, Conn., a corporation of Connecticut Application January 4, 1951, Serial No. 204,341

21 Claims. (Cl. 73-32) This invention relates to instruments for sensing the densities of fluids.

There are many occasions on which it is desirable to sense the density of fluids by generation of density-responsive power of a magnitude sufficient to operate an indicator or an aggregate of an indicator or computer drive under various conditions under which the heretofore-known density-sensing instruments would and could not perform. By way of example, the reliable sensing of the density of fuels in aircraft installations, both in the air and on the ground, was a long-felt need in order to measure a fuel-supply by its weight, rather than by its volume, for the ultimate purpose of obtaining an accurate and directindication of the potential power in the fuel of the supply without having to take various grades of fuel and varying atmospheric temperatures and pressures into consideration. The

heretofore-known density-sensing instruments are by no means satisfactory for this and other purposes, not only because they fail to generate even a fraction of the power required to operate an indicator or an a regate of an indicator or computer drive, especially where the indicator is rather remote from the fluid-testing location, but also because they fail to perform satisfactorily under frequently unavoidable conditions of vibration, acceleration and deceleration, and also when they are tilted into different positions, as in aircraft in flight or in portable or rollable equipment, for instance.

Accordingly, it is one of the main objects of the present invention to provide a fluid-density sensing instrument which is devoid of any of the above-mentioned shortcomings of the heretofore available or known instruments of this general type, thereby to render the instant instrument practical and advantageous for the above-mentioned and other purposes in mind.

A further object of the present invention is to provide a density-sensing instrument which gencrates a density-responsive power of exceptionally large magnitude that will assuredly operate an indicator or an aggregate of an indicator or computer drive under all conditions.

Another object of the present invention is to provide an instrument of this type which will accurately sense the density of a fluid even under exceptionally severe conditions of shock or vibration.

It is another object of the present invention to provide an instrument of this type which will accurately sense the density of a fluid regardless of any position the instrument may assume.

thereby rendering the instrument suited especially, though by no means exclusively, for use in air-. craft.

A further object of the present invention is to provide an instrument of this type which performs accurately and reliably even when subjected, while in motion, to most rapid acceleration or deceleration, thereby even further enhancing its use in aircraft or other movable equipment.

It is still a further object of the present invention to provide an instrument of this type which is a self-contained unit of small bulk and simple and sturdy construction, yet is highly accurate and reliable in performance, and readily lends itself to efficient mass production at relatively low cost.

Other objects and advantages will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

Fig. 1 is a side elevation, partly in section, of a density-sensing instrument embodying the present invention;

Fig. 2 is an enlarged longitudinal section through the same instrument;

Fig. 3 is a section takenon the line 3-3 of Fig. 2;

Fig. 4 is an elevational view of a. density-sensing instrument embodying the present invention in a modified manner;

Fig. 5 is a top plan view of the modified instrument;

Fig. 6 is an enlarged longitudinal section through the modified instrument as taken on the line 66 of Fig. 5;

Figs. 7 andB are enlarged fragmentary sections taken on the lines '!'I and 8-8, respectively, of Fig. 6; and

Fig. 9 is a fragmentary section taken on the line 99 of Fig. '7.

Referring to the drawings, and more particularly to Figs. 1 and 2 thereof, the reference numeral I ll designates a density-sensing instrument which comprises, in the present instance, an outer casing H and a centrifuge l2 therein. The cas ing I l is, in this instance, formed by a cylindrical member l3, and top and bottom covers I4 and I5, respectively, which are suitably secured to the cylindrical member I3, as by bolts [6 and IT, for instance. To seal the casing l I, there are preferably interposed between the cylindrical member 13 and the covers i4 and I5 gaskets it and !9, respectively. Fluid f is, in the present instance, admitted into and discharged from the casing H through an inlet and an outlet respectively, in the top cover it.

The centrifuge l2 comprises, in the present instance, a rotary container or bucket 23 which is preferably closed at its open top by a suitably secured cover 24 thereon. The bucket 23 is provided with a depending shank 25, having a reduced end 26 which is journaled, in this instance, in an an'tifriction hearing or bearings iii in a spider 28 which may suitably be secured at 29 to the bottom cover 15. The cover 24 on the bucket 23 is provided with a sleeve-type extension 30 which, in this instance, is also journaled in antifriction hearing or bearings in top cover I iof the casing H. The sleeve-extension 30 on the cover 24 extends to the outside of the casing ll through an aperture hid in the top cover [4 thereof, and the aperture [411 is sealed from the outside by a packing a in a packing-holder 36 on the top cover 14. For driving the bucket 23, the end of the shank 25 of the same may conveniently be flattened as at 32 in order to form the driven-element of a coupling 33 of which the driving-element 34 is provided with a recess 35 with which the drivenelement is in registry. The driving-element 34 of the coupling 33 is journaled in preferably antifriction-type bearings 31 and 38 in a packingcase 39 and a packing-retainer 46, respectively. The packing-case 39 may suitably be secured, as by bolts 4|, to the bottom cover [5 of the casing I I, while the packing-retainer 4:] is secured by bolts 42 to the packing-case 39. The packing-case 39 is provided with a preferably annular recess 43 wherein one or more packingglands 44 are compressed between the retainer 4!] and a deflector-ring 45 so as to be held in firm engagement with the coupling-element 34 to prevent leakage of fluid past the latter. The coupling-element 34 may at its outer end be coupled at to an electric motor or any other suitabl prime mover (not shown).

As best shown in Figs. 2 and 3, the cover 24 on the bucket 23 is provided with several preferably equiangularly-spaced pairs of depending lugs 5| which pivotally receive at 52 the ends 53 of several arms 54, respectively. Depending from the end 53 of each arm 54 is a stud 55 which carries a rigid body-member 51. Each of the body-members 51 is, in the present instance, hollow and of spherical shape, having a diametrically-extending tubular core 56 through which the respective stud 55 extends, and each body-member 51 is retained on its respective stud 55 by nuts 58 on the latter. In the present instance, there are provided four arms 54 with their respective body-members 51, and the free end of each arm 54 is provided with a follower 59 which rides between spaced collars 6B and 6| on a spindle 62 that is axially movable with its ends in a central bore 63 in the bucket 23 and in the sleeve-extension 39 of the cover 24.

In order to counteract the centrifugally-acting forces of the body-members 51 when the fluidcharged centrifuge is spinning, there are provided balanced and pre-loaded springs 64 and 65 which, in this instance, are compression-type springs arranged in the manner shown in Fig. 2. The centrifuge I2 is provided with one or more fluid-inlet ducts 6'! and one or more fluid-outlet ducts 53, so that the centrifuge will hold the. same fluid as the casing ll.

remain constant. i will, of course, change with varying atmospheric The principle underlying the present instrument is derived from the equation of the centrifugal force of a rotating body. Thus, the centrifugal force of a rotating body is:

wherein:

This equation may be used as follows in order to determine the centrifugally-acting forces of the body-members 51 in the fluid-holding centrifuge.

l rlfiilfillid wherein SB=density of body members 51, SF=density of fluid.

It follows from the latter equation that all factors involved in determining the centrifugallyacting forces of the body-members 51, with the exception of SF (density of fluid) are constants, assuming thereby that the rotational velocity N of the body-members and the distance r between their centers and the center of rotation The density SF of the fluid temperature and pressure conditions, also with the introduction of different fluids into the centrifuge. It also follows from the above equation that the centrifugally acting forces of the body members 57 have positive values when the density of the fluid is lower than that of the body members 5?, meaning that the latter will have a tendency to move outwardly from their normal rest position shown in Fig. 2 and further explained hereinafter. On the other hand, the centrifugal acting forces of the body members have negative values When the density of the fluid is higher than that of the body members 5?, meaning that the latter will have a tendency to move inwardly from their normal rest position in Fig. 2. In the latter event, the forces acting on the body members are in reality centripetal forces, but they are nevertheless referred to hereafter as centrifugal forces although they have negative values. Hence, the difference in the densities of the fluid and body members, respectively, in the centrifuge is directly proportional to the centrifugally-acting forces of the body-members 51, with the proviso that plus and minus values of these forces denote lower and higher densities, respectively, of the fluid than that of the body members.

The present invention contemplates to counteract the centrifugally-acting forces of the bodymembers, whether positive or negative, with a force which varies with the latter forces, and to utilize the counteracting force for perceptibly sensing the density of the fluid in the centrifuge. In the instant instrument l0, the positive and negative centrifugally-acting forces of the bodymembers 5'! are counteracted by the forces of the compression-springs and 64, respectively, and their displacement from their normal balanced rest position (Fig. 2) is an accurate measure of the density of the fluid in the centrifuge, as will be readily understood. It is the balancing force of the springs 64 and 65 which holds the body members 51 in the normal rest position shown in Fig. 2 when the centrifuge I2 is at rest, and it appears from the foregoing equation that the centrifugal forces of the body members will be zero when the density of the fluid f in the spinning centrifuge equals that of the body members 51, in which event the latter will remain in the position shown in Fig. 2 when the centrifuge i driven. Whenever the density of the fluid in the centrifuge deviates from that of the body members 51, the same displacement as that of the counteracting springs 64 and '65 is imparted also to the spindle 62 by virtue of its specific interposition in the operating connection between the springs 64, 65 and the body-members 51, wherefore the axial displacement of the spindle 52 from its normal position (Fig. 2) in either direction also affords an accurate indication of the density of the fluid in the centrifuge. Thus, the density of the fluid in the centrifuge may directly be read by the spindle 62, or an extension thereof, against a properly calibrated scale (not shown), or the spindle 62 may form the drivin" member of an aggregate of an indicator or com-- puter drive.

The centrifuge I2 is driven at the same constant speed, and the body-members 51 may be displaced outwardly or inwardly from the normal rest position shown in Fig. 2, depending on the density of the fluid in the centrifuge, as wil be readily understood. While the displacement of the body-members 5'! by their centrifugellyacting forces entails some variation in the value of the factor 1' in the foregoing equation of-these forces, this variation of r may safely be disregarded as it hardly aifects the degree of the density of a fluid obtained by the present instrument.

In order that the centrifugally-acting forces of the body-members may be of sufficient magnitude to meet the objectives of generating a density-responsive power of large magnitude, as well as rendering the instrument, insofar as its correct performance is concerned, immune to vibration, shock, acceleration and deceleration, and tilting into any position, it is indicated by the foregoing equation of these centrifugallyacting forces to have body-members of large volumes. It is for this reason that the bodymembers 51 are preferably in the form of relatively large-size members which may be made hollow so as to encounter little difiiculty with presently available rigid materials to keep their density at approximately that of the fluids to be tested.

the same. Further, by being provided with the fluid-inlet 20 and fluid-outlet 22 in the casing II, and with the inletand outlet-ducts 61 and 63, respectively, in the centrifuge 12, the present instrument may be in by-pass communication with a fluid-delivery line, for instance, to sense the density of the fluid and its density-variations under varying temperature and pressure conditions over an extended period of time. The present instrument is, for the foregoing reasons, suited especially, though by no means exclusively, for use in aircraft installations or other portable or rollable equipment. The present instrument is, for instance, admirably suited for use in aircraft installations for the purpose of measuring a fuel supply by its weight, rather than by its volume, for the ultimate purpose of obtaining an accurate and direct indication of the potential power in the fuel of the supply without having to take varying grades of fuel and varying atmospheric temperature and pressure con ditions into consideration. To accomplish this, the instant instrument may be combined with a volumetric flow-meter for computing the weight of a quantity of fuel in a manner similar to that shown in the patent to Reeve, No. 1,278,077, dated September 3, 1918.

It will be observed from Fig. 2 that the bucket 23 of the centrifuge I2 is closed by the cover 24, so as to entrap the fluid therein and cause it to spin with the bucket at the same, or substantially the same, speed.-Also, while the ducts 6'! and 68 in the centrifuge are kept relatively small in size so as to accomplish the objective of entrapment of the fluid in the centrifuge for the above-mentioned purpose, they nevertheless permit substantial circulation of the fluid through the centrifuge,

Since the centrifugally-acting forces of the body-members are, as hereinbefore explained. quite considerable, it follows that the spindle 62 will without fail be shifted into a corresponding axial position even if the same should encounter considerable resistance by an indicator or an aggregate of an indicator or computer drive with which the spindle 62 may be operatively connected. Also, since the sensing of the density of the fluid in the instrument is responsive to the displacement of the body-members 51 therein in consequence of their centrifugally-acting forces, the instant instrument is also immune to even severe shock or vibration insofar as its reliable and accurate performance is concerned. Moreover, the instant instrument may be tilted or inverted into any position without in any way adversely affecting the correct performance of especially since the fluid-inlet ducts 6! are nearer the rotary axis of the centrifuge than the fluidoutlet ducts 68 so that the varying pressures of the fluid in the centrifuge will induce fluid-circulation therethrough.

The instant instrument H), which is a self-contained unit effectively sealed against leakage of fluid therefrom, may readily be disassembled for the inspection, repair or replacement of any part or parts thereof. Thus, the covers l4 and I5 may readily be removed from the cylindrical member l3 of the casing l I for access to, or removal of, the centrifuge l2. The centrifuge l2 is another selfcontained unit which may readily be disassembled for the inspection, repair or replacement of any part or parts thereof.

The instant instrument H3 is adapted for sensing the densities of all kinds of fluids, and it is to be understood that the term fluid as used herein connotes liquids and gases, as Well as finely-divided solids capable of flowing.

While in the hereinbefore described instrument It the density of a fluid therein is in the final analysis indicated by axial motion of the spindle 62, the density of a fluid in a modified instrument is) is indicated by rotary motion of a spindlemember ll (Figs. 4 to 6). This modified densitysensing instrument Til comprises, in the present instance, a casing 12, a centrifuge 13, and a motion-transmitter M.

The casing 72 is, in this instance, of general cup-shape, and is closed at the top thereof by a cover F5 which may suitably be secured thereto, as by screws 18, for instance (Fig. 5). The casing 12 is provided with a fluid-inlet l1 and a fluidoutlet l8. To prevent leakage of fluid 1 from the interior of the casing 12, a gasket 8| is preferably interposed between the top of the casing I2 and the cover 75 thereon.

The centrifuge i3 is, in this instance, in the form of an inverted bucket 82 which is closed at its open end by a suitably secured cover tit. The bucket 82' is rotatably mounted in the casing '12 by having a shank on its cover 33 and a pressfitted or otherwise secured sleeve 85 in its bottom 86 journaled in antifriction bearings 8'! and 88, respectively. The bearing 8'] may be provided in a spider on the bottom wall 98 of the casing 12, while the bearing may be provided in a bracket es in the casing 72.

The bucket 82 is driven or spun by any suitable prime mover (not shown) through intermediation of a magnetic coupling d2 having the driving and driven elements and 9d, respectively. The driving-element of the coupling e2, which is in the form of a cup-shaped member 55 carrying a permanent magnet or magnets 96, is provided with a shaft-extension 9'5 which is journaled in a bearing SE in a hood or cap over the bottom of the casing '52. The driving-element 9-3 of the coupling is preferably provided with a wear-ring I!) of steel or the like, which coop rates with the outer races of a plurality of preferably equisingularly-spaced antifriction bearings Isl (at least three) that are carried by studs I62, respectively, on the bottom wall 92} of the casing 72. Thus, the bearings IE! and the bearing 93 cooperate in rotatably supporting the couplingelement 93 relative to its companion element 94. The companion element St is provided by the shank 84 of the cover 82-5 and a permanent magnet or magnets I33 thereon. As shown in Fig. 6, the coupling-element t l extends into a depressed wall-portion Ifid of the casing 72, and is in magnetic driving relation with the companion element 93. For efiicient performance of the magnetic coupling 92, the casing i2 is preferably made from a nonmagnetic material, such as aluminum or an aluminum alloy, for instance.

Provided in the centrifuge I3 are several identical body-members ltd, in th present instance four, which, in contrast to the previously-described spherical body-members 5?, are elongated hollow members, each being provided with an axially-extending tubular core lb! through which extends a stud 588 on which the respective bodymember 5% is mounted with the aid of nuts I09. Each of the studs N38 is provided with a blocktype head Iit which is pivotally mounted at III in a bearing-block H2 on the cover 83 of the bucket 82 (see also Fig. 7). Thus, the bodymembers liit are swingable inwardly and outwardly about their respective pivot-supports II I. Pivotally connected at IE3 with each stud I08 is a bar I Hi, having a rack-portion l !5 in permanent mesh with a spur gear I Hi on a spindle Ill (Figs. 6 and '7) which is mounted with one end in a combination thrust-and-journal bearing I I8 on the cover 83 of the bucket 82, and is journaled with its opposite end in the sleeve 85 on the bucket 32. Endwise motion of the spindle H1 is prevented by the gear Ilfi which is in close proximity to the adjacent end of the sleeve 85 (Fig. 6). The bars IM- are received for longitudinal movement in guideways I2fl, respectively, in a cage I2I which is freely slidable on the spindle II! relative to the gear IIt thereon. The guideways i23 in the cage I2I are so coordinated that the rack-portions N5 of the bars 5 id therein are in permanent mesh with the gear Ht on the spindle I ll, as is clearly shown in Fig. 7. By virtoe of the longitudinal guidance of the bars Ii in the cage I2 I, the latter will float on the spindle I I1, upwardly or downwardly, as the body-members swing to and from their normal position of rest, respectively (Fig. 6).

To counteract the centrifugally-acting forces of the body-members I05 when the fluid-holding centrifuge spins, there are provided balanced and pre-loaded torsion-springs I23 and E24 which are anchored with their inner ends on the spindle II! and with their other ends on studs I25 and I253, respectively, on the cover 83 of the bucket 82. The turns of the springs I23 and I25 expand in opposite directions so that the latter oppose each other. I

Fluid from the casing '52 is admitted into the bucket 82 through inlets I33 in the bottom wall 88 of the latter, and fluid may be discharged from the bucket 82 through outlets IZ-iI in the cover 83 thereof. It will be noted in Fig. 6 that the fluid-inlets I39 are closer to the rotary axis of the centrifuge it than the fluid-outlets I35 therein, wherefore circulation of fluid through the centrifuge will be induced when the latter spins.

Any outward or inward displacement in the fluid-holding centrifuge of the body-members I86 from their rest position by centrifugally-acting forces (Fig. 6) entails rotary motion of the spindle H1 in opposite directions, respectively, through intermediation of the bars Ii4 with their rack-portions H5 and the gear Hi5 on the spindle Ill. The gear I It is of such width as to remain in permanent mesh with the rack-poi tions H5 of the bars IIG throughout the limits of displacement of the body-members IE6 in the centrifuge i3.

Rotation in either direction of the spindle H7, in consequence of displacement of the bodymembers see only and not in consequence of its rotation with the centrifuge, is transmitted to the spindle-member "H through the motiontransmitter T4. To this end, the sleeve on the bucket 82 and the upper end of the spindle Hi carry gears Mi? and I39, respectively, of which gear I46 is in permanent mesh with a gear I li of a planetary gearing I62, having an opposed gear M3 which is drivingly connected with the gear I35 through intermediation of an idler gear I44 (Figs. 6 and 8). The idler gear Id i may rotatably be mounted on an inwar ly-projecting arm I45 of the bracket 9|, while the gears MI and I43 of the planetary gearing hi2 are freely rotatable on a preferably integral sleeve let of a gear-cage I4! which carries pairs of diametrically-opposite intermediate gears 143 and [59. respectively, which are identical. The gears MI and I43 are provided with preferably integral gears I 52 and I53, respectively, of which gear I52 is in permanent mesh with the intermediate gears IEt, and gear I53 is in permanent mesh with the inter .iediate gears 143 (Fig. 8). Further, the adjacent gears I48 and i553 of the pairs of intermediate gears are in permanent mesh with each other. The intermediate gears I48 and I5!) are rotatably mounted in opposite recesses E54 and I55 in the peripheral wall I58a of the cage I41, while the gears I52 and IE3 are received in said cage Nil. The cage IA! is further provided with a tranverse web flit from which the sleeve let extends in opposite directions (Fig. 6). Mounted in the sleeve MS of the cage I47 for rotation therewith is a stub-shaft I57 which is rotatably supported with its ends in suitable bearings I58 and I59 in the top and bottom walls I68 and I6I, respectively, of the bracket 9|. Carried by the stub-shaft I51 is a gear I62 which is in permanent mesh with a gear I63 on the depending shank I54 of the drivingelement I65 of a magnetic coupling I 56, the driven-element I61 of which is carried by the spindle-member 1|. The coupling-element I65, which is inside the casing 12 and journaled with its shank I84 in a bearing I68 in the top wall I60 of the bracket 9i, carries a permanent magnet I69 which is in magnetic driving relation with a permanent magnet I of the companion element I61 outside the casing 12. The spin-- dle-member 1!, which carries the driven element I 61 of the coupling I66, is journaled in a bearing or bearings I1I in a block I12 which is suitably mounted at I13 on a spider I14 that is, in turn, mounted on the top cover 15 of the casing 12 by screws I15, for instance. The bracket 9| is located in the casing 12 against rotation therein by a dowel pin or pins I18, and is securely held therein by several leaf-type springs I11 on the top cover 15 of the casing 12.

The gearing I42 is a typical planetary gearing in which the gear-cage I41 (that carries the intermediate gears I48 and I58 and the gear I62) will remain at rest as long as the gears MI and I43 are turned at the same angular speed in opposite directions, respectively. Hence, the ratios between the gears I40 and MI and between the gears I39 and I43 are the same (oneto-one in the present instance), and gear M3 is driven in a direction opposite to that of the gear I M by virtue of the interposition between the former andthe gear I39 of the idler gear ltd.

On displacement of the body-members H36 in the centrifuge 13 from their normal rest position (Fig. 6), by the centrifugally-acting forces thereon, the spindle III will be turned in either direction, depending on the direction of displacement of the body-members I66 from their normal rest position. Rotary motion. of the spindle I I1 in consequence of the displacement of the body-members I06 in the centrifuge will result in rotation of gear I43 at an angular speed which is different from the invariable angular speed of the gear I4! (assuming that the centrifuge is spun at a constant speed), with the result that the gear-cage I41 is turned about its rotary axis in a direction and to an extent commensurate with the displacement of the bodymembers I56 in the centrifuge. This rotation of the gear-cage I41 in response to the displacement of the body-members I66 in the centrifuge Will be transmitted to the spindle-member H through the meshing gears I62 and I63 and the magnetic coupling I66.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered'in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

I 01am 7 a I 1. A density-sensing instrument,. comprising a rotary container adapted to hold fluid; driving-means for said container; a rigid body in said container movable toward and away from the rotary axis thereof and having a density approximating those of fluids that may be. density-tested in said container; and-a device including resiliently deformable means for holding said body in a normal position within said conl0. tainer while the latter is not driven, and yieldingly resisting outward and inward movement of said body from said normal position in the spinning fluid-holding container, whereby the deformation of said means affords an indication of the density of fluid in said container.

2. The combination in a density-sensing instrument as set forth in claim 1, in which said body has a relatively large volume and is hole low so as to have said approximate density.

3. A density-sensing instrument, comprising a rotary container adapted to hold fluid; drivingmeans for said container; a rigid body in said container movable toward and away from the rotary axis thereof and having a density approximating those of fluids that may be density tested in said container; a density-registering element movable independently of the rotation of said container; an operating connection between said element and body for translating centrifugal displacement of the latter in the fluid-holding container into movement of said element of proportional magnitude; and resilient means resisting said centrifugal displacement of said body.

4. A density-sensing instrument, comprising a support; a container rotatably mounted on said support and being adapted to hold fluid; driving-means for said container; a rigid body in said container movable toward and away from the rotary axis thereof and having a'density approximating those of fluids that may be density-tested in said container; a densityregistering element externally of said container and supported for movement independently of the spinning container; an operating connec-- tion between said element and body for translating centrifugal displacement of the latter in the fluid-holding container into movement of said element of proportional magnitude; and resilient means resisting said centrifugal displacement of said body.

5. A density-sensing instrument as set forth in claim 4, in which said element is reciprocable, and said operating connection translates inward and outward displacements of said body into reciprocation of said element of proportional magnitude and in opposite directions, respectively.

6. A density-sensing instrument as set forth in claim 4, in which said element is rotatable in opposite directions, and said operating connection translates inward and outward displace ments of said body into turning motions of said element of proportional magnitude and in said opposite directions, respectively.

7. A density-sensing instrument, comprising a casing adapted to hold fluid; a closed container rotatably mounted in said casing and having a duct to provide communication between the interiors of said casing and container; drivingmeans for said container; a rigid body in said container movable toward and away from the rotary axis thereof and having a density approximating those of fluids that may be densitytested in said container; a density-registering element externally of said casing and supported for movement independently of the spinning container; an operating connection between said element and body for translating centrifugal displacement of the latter in the fluid-holding container into movement of said element of proportional magnitude; and spring-means resiliently resisting said centrifugal displacement of said body.

8. A density-sensing instrument, comprising a casing adapted to hold fluid and having a fluidinlet and a fluid-outlet; a closed container rotatably mounted in said casing and having ducts differently spaced from the rotary axis of said container to provide communication between the interiors of said casing and container; drivingmeans for said container; a rigid body in said container movable toward and away from the rotary axis thereof and having a density approximating those of fluids that may be densitytested in said container; a density-registering element externally of said casing and supported for movement independently of the spinning container; an operating connection between said element and body for translating centrifugal displacement of the latter in the fluid-holding container into movement of said element of proportional magnitude; and spring-means resiliently resisting said centrifugal displacement of said body.

9. A density-sensing instrument as set forth in claim 8, in which said body is guided in said container for movement toward and away from the rotary axis thereof.

10. A density-sensing instrument as set forth in claim 8, in which said body is pivotally mounted in said container for rocking motion about an axis transverse to the rotary axis of the latter. 11. A density-sensing instrument as set forth in claim 8, in which said spring-means act di rectly on said operating-connection so that the latter will resiliently resist said centrifugal displacement of said body.

12. A density-sensing instrument as set forth in claim 8, in which said driving-means comprise a magnetic coupling having driving and driven elements externally and internally of said casing, respectively, in magnetic driving relation with each other, and said driven element is drivingly connected with said container.

13. A density-sensing instrument, comprising a casing adapted to hold fluid; a closed container rotatably mounted in said casing and having ducts diflerentially spaced from the rotary axis of said container. to provide communication between the interiors of said casing and container; driving-means for said container; a rigid body pivotally mounted in said container for rocking motion about an axis transverse to the rotary axis of the latter, said body having a density approximating those of fluids that may be density 14. A density-sensing instrument, comprising" a closed casing adapted to hold fluid and having a fluid-inlet and a fluid-outlet; a closed container rotatably mounted in said casing and. having ducts differently spaced from the rotary axis of said container to provide communication between the interiors of said casing and container; driving-means for said container; a plurality of identical rigid bodies pivotally mounted in angularly-spaced relation in said container at identical distances from the rotaryaxis of thelattor for rocking motion about axes, respectively,

which extend transversely of said'rotary axis, said bodies being provided with followers, respectively, and each body having the same density approximating those of fluids that may be densitytested in said container; a spindle longitudinally reciprocable in said container coaxially thereof and extending to the outside of said container and easing, said spindle having in its periphery an endless groove in which said followers of said bodies are received for moving said spindle in opposite directions on inward and outward movements of said bodies, respectively; and opposed balanced springs resiliently resisting axial movement of said spindle from a certain intermediate position in either direction.

15. A density-sensing instrument, comprising a support; a container rotatably mounted on said support and being adapted to hold fluid; drivingmeans for said container; a rigid body mounted in said container for movement toward and away from the rotary axis thereof and having a density approximating those of fluids that may be density-tested in said container; a spindl journaled in said container for independent rotation coaxially thereof; an operating connection between said body and spindle for turning the latter in opposite directions on inward and outward motions of the former, respectively, in said container; an elastic coupling between said container and spindle; planetary gearing on said support having independently coaxially turnable first gears and an intermediate gear in mesh with, and bodily movable in an epicycloidal path about the common rotary axis of, said first gears; equalratio driving connections between said container and one of said first gears and between said spindle and the other one of said first gears, respectively, for driving said first gears in opposite directions, respectively; a rotatable density-registering element; and an operating connection between said intermediate gear and element for translating bodily motion of the former into rotary motion of the latter of proportional magnitude and in a corresponding direction.

16. A density-sensing instrument, comprising a closed casing adapted to hold fluid and having a fluid-inlet and a fluid-outlet; a closed container rotatably mounted in said casing and having ducts differently spaced from the rotary axis of said container to provide communication between the interiors of said casing and container; a rigid body mounted in said container for movement toward and away from the rotary axis thereof and having a density approximating those of fluids that may be density-tested in said container; a spindle journaled in said container for independent rotation coaxially thereof and extending with one end into said casingfa first operating connection between said body and spindle for turning the latter in opposite directions on inward and outward motions of the former, respectively, in said casing; an elastic coupling between said container and spindle; planetary gearing in said casing having independently coaxially turnable first gears and an intermediate gear in mesh with, and bodily movable in an epicycloidal path about the common rotary axis of, said first gears; equal-ratio driving connections between said container and one of said first gears and between said spindle end and the other one of said first gears, respectively, for driving said first gears in opposite directions, respectively; a rotatable density-registering element externally of saidcasing; and a second operating connection between said intermediate gear and element for translating bodily motion of the former into rotary motion of the latter of proportional magnitude and in a corresponding direction.

17. A density-sensing instrument as set forth in claim 16, in which said second operating connection includes a magnetic coupling having driving and driven elements internally and externally of said casing, respectively, in magnetic driving relation with each other.

'18. A density-sensing instrument as set forth in claim 16, in which said body is pivotally mounted in said container for rocking motion about an axis transverse to the rotary axis of the latter, and said first operating connection includes a further gear on and turnable with said spindle, and a rack in mesh with said further gear and connected with said body remote from its pivot axis.

19. A density-sensing instrument as set forth in claim 16, in which said body is pivotally mounted in said container for rocking motion about an axis transverse to the rotary axis of the latter, and said first operating connection includes a further gear on and turnable with said spindle, a cage axially slidable on said spindle and having a guideway, and a rack in mesh with said further gear, said rack being received in said guideway and restrained thereby against movement relative thereto other than longitudinal movement transversely of said spindle, and being pivotally connected with said body remote from the pivot axis of the latter.

20. A density-sensing instrument as set forth in claim 16, in which there is provided a plurality of said rigid bodies which are identical in size, shape and weight and pivotally mounted in angularly-spaced relation in said container at equal distances from the rotary axis of the latter for rocking motion about axes, respectively, at right angles to said rotary axis, and said first operating connection includes a spur gear on and turnable with said spindle, a cage axially slidable on said spindle and having guideways, and racks in mesh with said spur gear, said racks being received in said guideways, respectively, and restrained thereby against movement relative thereto other than longitudinal movement perpendicular to said spindle, and being pivotally connected with said bodies, respectively, remote from the pivot axes of the latter.

21. A density-sensing instrument as set forth in claim 16, in which said elastic coupling is formed by opposed pre-loaded spiral torsion springs anchoredwith their inner ends to said spindle and with their outer ends to said, container.

DENNISON H. MACDONALD.

References Cited in the file of this patent UNITED STATES PATENTS Number 

